Pillar[5]arenes, a new class of fascinating cyclophanes, continue to attract the attention of chemists and the interest in this class of macrocycles continues unabated primarily due to their enormous application potential in diverse areas. The most notable feature of pillar[5]arenes is their deep π-encircled internal cavity capable of accommodating guest molecules through diverse non-covalent interactions, thereby raising the hope of developing molecular sensors. It is noteworthy that by virtue of their structural architecture, cycloquinones decorated with deep internal cavity essential for molecular sensing, are also being increasingly explored for the development of molecular sensors featuring redox active properties.
A recently reported quinone-based, redox-active resorcin[4]arene cavitand is one such candidate which is able to form kinetically stable host-guest complexes whose binding strength can be modulated by changing the redox state of the cavitand. However, the quinone rings in the aforesaid system do not form part of the cyclamer backbone. Pillar[5]quinone is structurally unique in this respect not only because of the fact that all the five quinone rings are part of the cyclamer backbone, but also due to the symmetrical crowning of the periphery by ten carbonyl oxygen atoms.
Article Titled “A computational study of unique properties of pillar[n]quinones: self-assembly to tubular structures and potential applications as electron acceptors and anion recognizers” by Lao K U et al. publishes in J Comput Chem. 2011, 32(12), 2716-26 reports computational studies that have suggested that pillar[5]quinone could showcase intramolecular charge transfer upon excitation of electrons from HOMO to LUMO, owing to the large difference in the electron distribution between them. Furthermore, pillar[5]quinone-derived systems have been predicted to be promising candidates for trapping anionic halogens. Computational models employed to study pillar[5]quinone predicted these compounds to be an efficient electron acceptor. Also, the theoretical studies anticipated that pillar[5]quinone can efficiently trap anions by CH-π interactions. Bromide and chloride can fit inside the pillar[5]quinone. Computational studies also foresaw the possibility of supramolecular tubular aggregation of monomeric pillar[5]quinone by CH—O interactions.
Article Titled “A Facile and Efficient Preparation of Pillararenes and a Pillarquinone” by Derong Cao et al. published in Angewandte Chemie International Edition, 2009, 48 (51), 9721-9723 reports a facile and efficient preparation of pillararenes and a pillarquinone as shown below:

The above process for the synthesis of pillar[5]quinone uses eerie ammonium nitrate (CAN) as an oxidant and the presence of heavy metal in CAN is environmentally hazardous also one of the reactants viz. 2,5-bis(benzyloxymethyl)-1,4-diethoxybenzene is not commercially available and hence it has to be synthesized. Pillar[5]quinone a red colored molecule is isolated by soxhlet extraction using DCM, owing to its poor solubility.
However, the present invention provides an easy-to-operate, chromatography-free, economically and industrially feasible process for the preparation of pillar[5]quinone in multi-gram quantities by the oxone/iodobenzene-mediated oxidative de-aromatization of readily available 1,4-dimethoxypillar[5]arenes in good yields with less hazardous chemicals.